Direct drive seed metering device

ABSTRACT

A direct drive seed metering device for sowing machines operated by vacuum or high pressure and driven by a coaxial electric motor, comprising a seed metering disc for capturing seeds from a reservoir and laying them in a controlled manner in a furrow in the soil, where in the coaxial electrical motor couples directly and coaxially to the metering disc without the need for intermediate transmission elements, redactors, gears or timing belts, and where said coaxial electrical motor is a toroidal electric motor with a hollow rotor shaft, which fluidly connects said seed capturing means with a vacuum or high pressure generating means.

FIELD OF THE INVENTION

The present invention refers to a direct drive seed metering device andmore specifically to a seed metering device for sowing machines, drivenby an coaxial electric motor, comprising a seed metering disc forcapturing seeds from a reservoir and laying them in a controlled mannerin a furrow in the soil, where in the coaxial electrical motor couplesdirectly to the metering disc without the need for intermediatetransmission elements, redactors, gears or timing belts, thus increasingthe efficiency of the device.

In preferred embodiments of the present invention, the means forcapturing and releasing the seeds operate by vacuum or high pressure.

Additionally, preferred embodiments of the present invention comprise atoroidal electric motor with a hollow rotor shaft, through which theseed capturing means is fluidly connected to vacuum or pressuregenerating means

BACKGROUND OF THE INVENTION

Row crop sowing machines or seed planters for single seed sowing havebeen widely used for decades. Usually, said machines comprise at leastone rotating disc for holding and supplying the seeds to be planted andmeans for releasing and conducting the seeds to the furrows on theground at determined depths and spacing.

The rotating discs usually comprise holes, pockets, cradles or teeth forretaining the seeds with the help of vacuum or positive air pressurethat is interrupted at a desired point in order to let the seeds dropinto conducting means to the ground.

Most known sowing machines comprising a plurality of metering discs relyon only one driving assembly for simultaneously rotating all discs. Incase of machines comprising a large number of metering discs, e.g. 20 ormore, said driving assembly is bulky, complicated and expensive, notallowing the individual adjustment of the rotation of each meteringdisc, necessary in occasions when the sowing machine is not supposed tofollow a rectilinear path, wherein the more external sowing devices runfor a longer distance than the more internal ones.

Such drawbacks were addressed by the use of hydraulic systems fordriving individually each disc, comprising sophisticated electroniccontrol means, requiring both expensive and continuous maintenance.

Some late developments in sowing machines, replaced said hydraulicsystems by individual electric motors, leading to much simpler andeconomic equipment, as particularly disclosed in patent application WO2012/142607 A1 where the motors are connected to the axles of themetering discs.

Nevertheless, there is still a need for simpler metering devices, withreduced power requirements, and less expensive building and maintenance.

BRIEF DESCRIPTION OF THE INVENTION

The above mentioned drawbacks can be overcome and said needs fulfilledby the use of a seed distributing or metering device driven by a directdrive DC motor of the brushless type, high torque, and annular ortoroidal shape comprising a hollow shaft or annular rotor and coaxiallycoupled to the metering disc.

The application of a high torque motor directly coupled to therotational working elements of the seed metering device of the inventionreduces the need for reductions, gear transmissions, belt transmissionand other auxiliary transmission components found in seed meteringdevices known in the art. This reduction or complete elimination ofmechanical transmissions elements between the power source and the loadimplies a substantial reduction in power loss, which in turn results inimprovement in power output, reduced noise and vibrations, and allaround greater efficiency.

Additionally, the reduction or elimination of auxiliary transmissionelements greatly reduces maintenance costs and complexity, while alsoimproving the device operational life.

Furthermore, the slim design of the high torque, annular motor allowsfor the motor to be arranged partially or completely within the seedmeter housing, reducing the overall size of the device and partially orcompletely protecting the motor from outside elements.

Therefore, it is an object of the present invention to provide a seedmetering device for row crop sowing machines, also called seed planters,comprising:

-   -   a seed metering disc rotatable about a central shaft, having a        plurality of seed capturing and retaining means for capturing        and retaining the seeds,    -   a motor, which drives the seed metering disc,    -   releasing means for releasing the seeds from the seed capturing        and retaining means,    -   conducting means for conducting the released seeds onto the        ground, and    -   a housing for containing and protecting the metering disc,    -   wherein the motor is of the hollow-shaft type, toroidally shaped        and coaxially coupled to the metering disc.

In a preferred embodiment of the present invention, the hollow-shaftmotor is a direct drive DC motor of the brushless type.

In a preferred embodiment of the present invention, the seed capturingand retaining means are selected from the group comprising holes, cellsor cradles located near the outer perimeter of the metering disc.

In a preferred embodiment of the present invention, the seed capturingand retaining means consist of holes located near the outer perimeter ofthe metering disc and the hole size is determined by the type of seed tobe sown, so as to be able to retain the seeds in place until reachingthe releasing means.

In a preferred embodiment of the present invention, the metering disc isa cogwheel or gear, the teeth of which are the seed capturing andretaining means, where the teeth shape and the size of the gap betweenthe teeth being determined by the type of seed to be sown, so as to beable to retain the seeds in place until reaching the releasing means.

In a more preferred embodiment of the present invention, the housingcontaining the metering disc forms a vacuum chamber together with one ofthe faces of the metering disc, the device being provided with vacuumgenerating means for lowering the air pressure on said face of themetering disc so as to capture and retain the seeds within the seedcapturing and retaining means arranged on the face of the metering discopposite the vacuum chamber.

In a more preferred embodiment of the present invention, the housingcontaining the metering disc forms a high pressure chamber together withone of the faces of the metering disc, the device being provided withblowing means for increasing air pressure on said face of the meteringdisc so as to capture and retain the seeds within the seed capturing andretaining means arranged on the same face of the metering disc.

In a more preferred embodiment of the present invention, the devicefurther comprises a flexible sealing member contained within thehousing, which is sealingly attached to the inner wall of the housingand which is sealingly pressed against one face of the metering disc,thus defining a vacuum chamber, the device being provided with vacuumgenerating means for lowering the air pressure on said vacuum chamber soas to capture and retain the seeds within the seed capturing andretaining means arranged on the face of the metering disc opposite thevacuum chamber.

In a more preferred embodiment of the present invention, the devicefurther comprises

-   -   a concave plate within the housing, sealingly attached to one        face of the seed metering disc, and coupled to the hollow shaft        of the motor, thus defining a rotatable vacuum chamber,    -   vacuum generating means,    -   a non-rotatable tube or conduit, non-rotatably attached to the        housing, which passes through the housing and the hollow shaft        of the motor into the rotatable vacuum chamber, fluidly        connecting the vacuum means to the rotatable vacuum chamber.

In a most preferred embodiment of the present invention, the motor iscoupled to the seed metering disc by means of a hollow hub or othersuitable coupling means comprising a hollow shaft or tube, and whereinthe hollow hub is perforated, fluidly connecting the high pressurechamber or the vacuum chamber, where appropriate, to the hollow motorshaft of the motor coupled to said hollow hub.

In a most preferred embodiment of the present invention, the vacuumgenerating means or the blowing means are fluidly connected to thevacuum chamber or the high pressure chamber, where appropriate, throughthe hollow motor shaft of the motor and through the perforated hollowhub.

In a preferred embodiment of the present invention, the vacuumgenerating means or the blowing means are fluidly connected to saidvacuum chamber or high pressure chamber, where appropriate, through anopening or orifice in the housing in a position other than the hollowshaft—eccentrically regarding the metering disc—and wherein the couplingmeans coupling the motor to the seed metering disk does not allow fluidconnection between the vacuum chamber or high pressure chamber, whereappropriate, and the hollow shaft of the motor.

In a preferred embodiment of the present invention, the releasing meanscomprises a plate, fixed to the non-rotatable tube or conduit andlocated within the rotatable vacuum chamber, which makes contact with aregion of the face of the metering disc inside the rotatable vacuumchamber, blocking the orifices of the seed capturing and retaining meansand therefore interrupting the vacuum applied to the seeds retained onthe other face of the metering disk, making them drop into theconducting means towards the ground.

In a more preferred embodiment of the present invention, the vacuumchamber does not simultaneously overlap with all the seed capturing andretaining means of the metering disc and wherein the release of theseeds from the holes of the seed capturing and retaining means occurswhen a particular hole of the seed retaining means no longer overlapswith the vacuum chamber.

In a preferred embodiment of the present invention, the seed releasingmeans comprises a rotatable wheel contacting the metering disc on theface opposite the seeds capturing and retaining means, the wheelblocking the holes of the seed capturing and retaining means andtherefore interrupting the vacuum or pressure applied to the retainedseeds, making them drop into the conducting means towards the ground.

In a most preferred embodiment of the present invention, the motor ishoused within the housing, fixed to the inner surface of the housingwall.

In a preferred embodiment of the present invention, the motor is fixedto the outer surface of the housing wall.

In a preferred embodiment of the present invention, the seed releasingmeans comprise stationary or mobile brushes that physically remove theseeds from the seed capturing and retaining means.

In a preferred embodiment of the present invention, the device furthercomprises singulating means for allowing only one seed to be retained ineach capturing and retaining means.

In a preferred embodiment of the present invention, the singulatingmeans comprise a plate, parallel to the metering disc and spaced apartso as to allow only one seed to be retained in each capturing andretaining means.

In a preferred embodiment of the present invention, the conducting meansfor conducting the released seeds onto the ground comprises a conveyorbelt provided with bristles for guiding the seeds to an outlet close tothe soil and into an opened furrow in the soil.

In a preferred embodiment of the present invention, the conducting meansfor conducting the released seeds onto the ground comprises a tube forallowing the seeds to freely reach the soil by gravity, into an openedfurrow in the soil.

In a preferred embodiment of the present invention, the seed capturingand retaining means of the seed metering disc comprises holes and thehousing comprises a rotatable toothed wheel with a plurality of teeth orprojections, that engage with said holes of the seed capturing andretaining means as the disc rotates, removing obstructions and releasingseeds stuck in said holes.

In a most preferred embodiment of the present invention, the motor is alarge diameter annular torque motor with an annular rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a vacuum seed metering devicewherein the vacuum generating means are connected to the housing throughthe hollow motor shaft, according to a first embodiment of the presentinvention;

FIG. 2 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 1;

FIG. 3 is an exploded perspective view of a pressure seed meteringdevice wherein the blowing means are connected to the housing throughthe hollow motor shaft, according to a second embodiment of the presentinvention;

FIG. 4 is a schematic cross-section side view of the pressure seedmetering device of FIG. 3;

FIG. 5 is an exploded perspective view of a vacuum seed metering devicewherein the vacuum generating means are connected to the housing throughan air extraction conduit, according to a third embodiment of thepresent invention;

FIG. 6 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 5;

FIG. 7 is an exploded perspective view of a pressure seed meteringdevice wherein the blowing means are connected to the housing through anair intake conduit, according to a fourth embodiment of the presentinvention;

FIG. 8 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 7;

FIG. 9 is an exploded perspective view of a vacuum seed metering devicecomprising a vacuum chamber, according to a fifth embodiment of thepresent invention;

FIG. 10 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 9;

FIG. 11 is an exploded perspective view of a vacuum seed metering devicecomprising a rotating vacuum chamber, according to a sixth embodiment ofthe present invention;

FIG. 12 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 11;

FIG. 13 is an exploded perspective view of a vacuum seed metering devicecomprising a vacuum chamber connected to the vacuum generating meansthrough the hollow motor shaft, according to a seventh embodiment of thepresent invention;

FIG. 14 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 13;

FIG. 15 is an exploded perspective view of a pressure seed meteringdevice comprising a large diameter torque motor with an annular rotor,wherein the pressure generating means are connected to the housingthrough the annular rotor of the torque motor, according to an eighthembodiment of the present invention;

FIG. 16 is a schematic cross-section side view of the pressure seedmetering device of FIG. 15;

FIG. 17 is an exploded perspective view of a vacuum seed metering devicecomprising a large diameter torque motor with an annular rotor, whereinthe vacuum generating means are connected to the housing through theannular rotor of the torque motor, according to a ninth embodiment ofthe present invention;

FIG. 18 is a schematic cross-section side view of the vacuum seedmetering device of FIG. 17;

DEFINITIONS

To the effects of the present invention, the terms “fluid connection”,“fluidly connected”, “fluidly coupled” and variations of the same aremeant to be understood as connection or couplings that allow or maintainthe flow of fluids, and more particularly air, between the connectedelements.

For all of the embodiments described in the present invention, and anyother embodiment within the scope of the present invention, the term“atmospheric pressure chamber” is meant to the be understood as makingreference to a chamber that is neither the high pressure chamber nor thevacuum chamber. In some embodiments of the present invention, the“atmospheric pressure chamber” may be fluidly connected to the exteriorof the device through suitable fluid connection means, such as holes orconduits. Regardless of the above, the “atmospheric pressure chamber”may not be actually be at atmospheric pressure, but instead is used toidentify said chamber from the vacuum chamber or high-pressure chamberrespectively. More specifically, it refers to the chamber that is at ahigher pressure than the vacuum chamber in vacuum seed metering devices,or the chamber that is at lower pressure than the high pressure chamberin high pressure seed metering devices.

Likewise, the term “vacuum” is meant to be understood as a pressure thatis lower than the pressure in the atmospheric pressure chamber, and theterm “high pressure” is meant to be understood as a pressure that ishigher than the pressure in the

The terms “toroidal motor”, “annular rotor” and “torque motor” refer toelectrical motors whose rotor comprises a passing hole or orifice aboutits central axis.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described in more detail below, with reference tothe accompanying drawings that illustrate different exemplaryembodiments of the present invention.

For all of the following embodiments, while the hollow shaft electricmotor of embodiments 1 to 7 and the large diameter torque motor ofclaims 8 to 9 can be of any type of suitable electric motor with ahollow motor shaft, preferred embodiments of the present inventionutilize brushless DC electric motors.

Embodiment 1

FIGS. 1 and 2 show a vacuum seed metering device according to a firstembodiment of the present invention. Said vacuum seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 coupled about its central axis to a hollow rotor shaft 03.1 of acoaxially arranged motor 03 by means of a hollow hub 13 or othersuitable coupling means which allow the passage of air through it. Thestator 03.2 of the motor 03 is fixed to the interior of the housing 01by suitable fastening means (not shown). The hollow hub 13 is coupled tothe hollow motor shaft 03.1 by rods or pins 14 or other suitablefastening means. The metering disc 02 is coupled to the hollow hub 13 bya cotter pin 12 or other suitable securing means.

The metering disc 02 divides the housing 01 into two chambers; a vacuumchamber, fluidly connected to a vacuum generation means (not shown), andan atmospheric pressure chamber. Seeds 07 are loaded into a reservoir 21within the atmospheric pressure chamber through a seed inlet 06, whichmay or may not comprise a hopper and/or closure means (not shown).Vacuum is created in the vacuum chamber by the extraction of air in saidchamber by means of a vacuum generating means (not shown) through an airextraction outlet 05. Fluid connection between the vacuum generatingmeans and the vacuum chamber in the housing 01 is achieved through aplurality of orifices or holes 18 in the hollow hub 13 which connectsthe hollow motor shaft 03.1 of the motor 03 to the metering disc 02. Inturn, the hollow motor shaft 03.1 is fluidly connected to the airextraction outlet 05, which is connected to the vacuum generating means(not shown).

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the vacuum generated in the vacuum chamber by the vacuumgenerating means to capture seeds 07 from the seed reservoir 21 andretain them until the vacuum is interrupted by a wheel 09 or othersuitable seed releasing means, releasing the seed 07 from the holes 19of the metering disc 02, preferably into a seed outlet 10.

In a preferred embodiment the wheel 09 comprises a device arranged toblock or isolate the affected holes 19 from the vacuum generated by thevacuum generating means, causing the seed to be released from saidaffected hole 19. Preferably, the wheel 09 is made from a flexiblematerial, like rubber or other polymeric material, and located on theside of the metering disc 02 opposite to the seeds 07, which can isolatea particular hole 19 from the vacuum source.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity 17 within the housing 01, which doubles both as a cleaning devicefor cleaning and removing obstructions in the holes 19 and as anauxiliary means for releasing seeds 07 not properly released by the seedreleasing wheel 09. Preferably, the toothed wheel 11 is made fromflexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the wheel 09, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

Embodiment 2

FIGS. 3 and 4 show a pressure seed metering device according to a secondembodiment of the present invention. Said pressure seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 coupled about its central axis to a hollow rotor shaft 03.1 of acoaxially arranged motor 03 by means of a hollow hub 13 or othersuitable coupling means which allow the passage of air through it. Thestator 03.2 of the motor 03 is fixed to the interior of the housing 01by suitable fastening means (not shown). The hollow hub 13 is coupled tothe hollow motor shaft 03.1 by rods or pins 14 or other suitablefastening means. The metering disc 02 is coupled to the hollow hub 13 bya cotter pin 12 or other suitable securing means.

The metering disc 02 divides the housing 01 into two chambers; apositive pressure chamber, fluidly connected to a blowing means (notshown), and an atmospheric pressure chamber. Seeds 07 are loaded into areservoir 21 within the positive pressure chamber through a seed inlet06, which may or may not comprise a hopper and comprises sealing means(not shown). Pressure is created in the positive pressure chamber by thepressurization of air in said chamber by means of a blowing means (notshown), such as an air compressor, through a pressurized air inlet 05.Fluid connection between the blowing means and the positive pressurechamber in the housing 01 is achieved through a plurality of orifices orholes 18 in the hollow hub 13 which connects the hollow motor shaft 03.1of the motor 03 to the metering disc 02. In turn, the hollow motor shaft03.1 is fluidly connected to the pressurized air inlet 05, which isconnected to the blowing means (not shown).

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the pressure generated in the positive pressure chamber by theblowing means to capture seeds 07 from the seed reservoir 21 and retainthem until the pressure is interrupted by a wheel 09 or other suitableseed releasing means, releasing the seed 07 from the holes 19 of themetering disc 02, preferably into a seed outlet 10.

In a preferred embodiment the wheel 09 comprises a device arranged toblock or isolate the affected holes 19 from the pressure generated bythe blowing means, causing the seed to be released from said affectedhole 19. Preferably, the wheel 09 is made from a flexible material, likerubber or other polymeric material, and located on the side of themetering disc 02 opposite to the seeds 07, which can isolate aparticular hole 19 from the pressure source.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity (not shown) within the housing 01, which doubles both as acleaning device for cleaning and removing obstructions in the holes 19and as an auxiliary means for releasing seeds 07 not properly releasedby the seed releasing wheel 09. Preferably, the toothed wheel 11 is madefrom flexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the wheel 09, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

Embodiment 3

FIGS. 5 and 6 show a vacuum seed metering device according to a thirdembodiment of the present invention. Said vacuum seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 coupled about its central axis to a hollow rotor shaft 03.1 of acoaxially arranged motor 03 by means of a hub 13 or other suitablecoupling means. The stator 03.2 of the motor 03 is fixed to the interiorof the housing 01 by suitable fastening means (not shown). The hub 13 iscoupled to the hollow motor shaft 03.1 by rods or pins 14 or othersuitable fastening means. The metering disc 02 is coupled to the hub 13by a cotter pin 12 or other suitable securing means.

The metering disc 02 divides the housing 01 into two chambers; a vacuumchamber, fluidly connected to a vacuum generation means (not shown), andan atmospheric pressure chamber. Seeds 07 are loaded into a reservoir 21within the atmospheric pressure chamber through a seed inlet 06, whichmay or may not comprise a hopper and/or closure means (not shown).Vacuum is created in the vacuum chamber by the extraction of air in saidchamber by means of a vacuum generating means (not shown) coupled to anair extraction outlet 05 formed on or attached to the housing 01,fluidly connecting the vacuum generating means to said vacuum chamber.The hub 13 further provides a fluid seal over the hollow motor shaft03.1 of the motor 03, preventing fluid circulation of air through thehollow shaft 03.1 from and to the housing 01.

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the vacuum generated in the vacuum chamber by the vacuumgenerating means to capture seeds 07 from the seed reservoir 21 andretain them until the vacuum is interrupted by a wheel 09 or othersuitable seed releasing means, releasing the seed 07 from the holes 19of the metering disc 02, preferably into a seed outlet 10.

In a preferred embodiment the wheel 09 comprises a device arranged toblock or isolate the affected holes 19 from the vacuum generated by thevacuum generating means, causing the seed to be released from saidaffected hole 19. Preferably, the wheel 09 is made from a flexiblematerial, like rubber or other polymeric material, and located on theside of the metering disc 02 opposite to the seeds 07, which can isolatea particular hole 19 from the vacuum source.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity 17 within the housing 01, which doubles both as a cleaning devicefor cleaning and removing obstructions in the holes 19 and as anauxiliary means for releasing seeds 07 not properly released by the seedreleasing wheel 09. Preferably, the toothed wheel 11 is made fromflexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the wheel 09, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

Embodiment 4

FIGS. 7 and 8 show a pressure seed metering device according to a fourthembodiment of the present invention. Said pressure seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 coupled about its central axis to a hollow rotor shaft 03.1 of acoaxially arranged motor 03 by means of a hub 13 or other suitablecoupling means. The stator 03.2 of the motor 03 is fixed to the interiorof the housing 01 by suitable fastening means (not shown). The hub 13 iscoupled to the hollow motor shaft 03.1 by rods or pins 14 or othersuitable fastening means. The metering disc 02 is coupled to the hub 13by a cotter pin 12 or other suitable securing means.

The metering disc 02 divides the housing 01 into two chambers; apositive pressure chamber, fluidly connected to a blowing means (notshown), and an atmospheric pressure chamber. Seeds 07 are loaded into areservoir 21 within the positive pressure chamber through a seed inlet06, which may or may not comprise a hopper and comprises sealing means(not shown). Pressure is created in the positive pressure chamber by thepressurization of air in said chamber by means of a blowing means (notshown), such as an air compressor, through a pressurized air inlet 05formed on or attached to the housing 01, fluidly connecting the blowingmeans to said positive pressure chamber. The hub 13 further provides afluid seal over the hollow motor shaft 03.1 of the motor 03, preventingfluid circulation of air through the hollow shaft 03.1 from and to thehousing 01.

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the pressure generated in the positive pressure chamber by theblowing means to capture seeds 07 from the seed reservoir 21 and retainthem until the pressure is interrupted by a wheel 09 or other suitableseed releasing means, releasing the seed 07 from the holes 19 of themetering disc 02, preferably into a seed outlet 10.

In a preferred embodiment the wheel 09 comprises a device arranged toblock or isolate the affected holes 19 from the pressure generated bythe blowing means, causing the seed to be released from said affectedhole 19. Preferably, the wheel 09 is made from a flexible material, likerubber or other polymeric material, and located on the side of themetering disc 02 opposite to the seeds 07, which can isolate aparticular hole 19 from the pressure source.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity (not shown) within the housing 01, which doubles both as acleaning device for cleaning and removing obstructions in the holes 19and as an auxiliary means for releasing seeds 07 not properly releasedby the seed releasing wheel 09. Preferably, the toothed wheel 11 is madefrom flexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the wheel 09, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

Embodiment 5

FIGS. 9 and 10 show a vacuum seed metering device according to a fifthembodiment of the present invention. Said vacuum seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 coupled about its central axis to a hollow rotor shaft 03.1 of acoaxially arranged motor 03 by means of a hub 13 or other suitablecoupling means. The stator 03.2 of the motor 03 is fixed to the interiorof the housing 01 by suitable fastening means (not shown). The hub 13 iscoupled to the hollow motor shaft 03.1 by rods or pins 14 or othersuitable fastening means. The metering disc 02 is coupled to the hub 13by a cotter pin 12 or other suitable securing means.

A sealing member 15 is sealingly attached to the interior wall of thehousing 01 and is sealingly pressed against a face of the metering disc02, thus defining a vacuum chamber, while the remaining volume of thehousing 01 defines an atmospheric pressure chamber. The sealing member15 is made from a flexible material, like rubber or other polymericmaterial. The vacuum chamber is fluidly connected to a vacuum generationmeans (not shown), through an air extraction outlet 05 formed on orattached to the housing 01. The hub 13 further provides a fluid sealover the hollow motor shaft 03.1 of the motor 03, preventing fluidcirculation of air through the hollow shaft 03.1 from and to the housing01.

Seeds 07 are loaded into a reservoir 21 within the atmospheric pressurechamber through a seed inlet 06, which may or may not comprise a hopperand/or closure means (not shown).

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The sealingmember 15 is arranged over the face of the metering disc 02 so as tooverlap the vacuum chamber over some, but not all, the radially spacedholes 19.

The holes 19 utilize the vacuum in the overlapping vacuum chambergenerated by the vacuum generating means to capture seeds 07 from theseed reservoir 21 and retain them until the vacuum is interrupted,releasing the seed 07 from the holes 19 of the metering disc 02,preferably into a seed outlet 10. Interruption of the vacuum affecting aspecific hole 19 is achieved by rotating the metering disc 02 until saidspecific hole no longer overlaps with the vacuum chamber, thus releasingthe captured seed.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity 17 within the housing 01, which doubles both as a cleaning devicefor cleaning and removing obstructions in the holes 19 and as anauxiliary means for releasing seeds 07 not properly released by the seedreleasing mechanism. Preferably, the toothed wheel 11 is made fromflexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the seed holes 19 in the meteringdisc 02, and not removed by the curved plate 08, are carried over by therotating metering disc 02 until their respective seed holes 19 no longeroverlaps with the vacuum chamber, thus releasing the seeds 07 from themetering disc 02 and allowing them to freely fall through a seed outlet10, through a conducting means to an opened furrow on the soil oranother section of the seeding equipment.

Embodiment 6

FIGS. 11 and 12 show a vacuum seed metering device according to a sixthembodiment of the present invention. Said vacuum seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 sealingly attached to an concave plate 20 coupled about itscentral axis to a hollow rotor shaft 03.1 of a coaxially arranged motor03 by screws, bolts or other suitable fastening means 14. The stator03.2 of the motor 03 is fixed to the interior of the housing 01 bysuitable fastening means (not shown).

The metering disc 02 and the concave plate 20 define a rotating vacuumchamber, fluidly connected to a vacuum generation means (not shown)through a vacuum conduit 22. The remaining volume of the housing 01defines an atmospheric pressure chamber. Seeds 07 are loaded into areservoir 21 within the atmospheric pressure chamber through a seedinlet 06, which may or may not comprise a hopper and/or closure means(not shown).

The vacuum conduit 22, having a protruding hollow member 22.1, a flange22.2 and an air extraction outlet 05, is sealingly attached by itsflange 22.2 to the exterior of the housing 01 by means of screws 14,bolts or any other suitable fastening means. The protruding hollowmember 22.1 of the vacuum conduit 22 is inserted coaxially and throughthe hollow motor shaft 03.1 of the motor 03 and into vacuum chamberdefined by the metering disc 02 and the concave plate 20, providingfluid connection between said vacuum chamber and the vacuum generatingmeans (not shown) through the air extraction outlet 05. It should benoted that the protruding hollow member 22.1 of the vacuum conduit 22 isnot joined or attached to the hollow motor shaft 03.1 of the motor 03and thus does not rotate.

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the vacuum generated in the vacuum chamber by the vacuumgenerating means to capture seeds 07 from the seed reservoir 21 andretain them until the vacuum is interrupted by a plate 04 or othersuitable seed releasing means, releasing the seed 07 from the holes 19of the metering disc 02, preferably into a seed outlet 10.

The plate 04 is a plate made from a flexible material, like rubber orother polymeric material, located within the rotating vacuum chamber andnon-rotatably attached to the protruding hollow member 22.1 of thevacuum conduit 22 by means of a hub 13. The hub 13 is joined to theprotruding hollow member 22.1 of the vacuum conduit 22 by at least onerod or pin 16 or a suitable fastening means.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the plate 04, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

Embodiment 7

FIGS. 13 and 14 show a vacuum seed metering device according to aseventh embodiment of the present invention. Said vacuum seed meteringdevice comprises a cylindrical housing 01, which houses a rotatingmetering disc 02 coupled about its central axis to a hollow rotor shaft03.1 of a coaxially arranged motor 03 by means of a hollow hub 13 orother suitable coupling means which allow the passage of air through it.The stator 03.2 of the motor 03 is fixed to the interior of the housing01 by suitable fastening means (not shown). The hollow hub 13 is coupledto the hollow motor shaft 03.1 by rods or pins 14 or other suitablefastening means. The metering disc 02 is coupled to the hub 13 by acotter pin 12 or other suitable securing means.

A sealing member 15 is sealingly attached to the interior wall of thehousing 01 and is sealingly pressed against a face of the metering disc02, thus defining a vacuum chamber, while the remaining volume of thehousing 01 defines an atmospheric pressure chamber. The sealing member15 is made from a flexible material, like rubber or other polymericmaterial and contains an opening or orifice 15.1 formed on its innerwall. The vacuum chamber is fluidly connected to the hollow motor shaft03.1 of the motor 03 through said opening or orifice 15.1 formed on theinner wall of the sealing member 15 and through a plurality of orificesor holes 18 formed in the hollow hub 13, which connects said hollowmotor shaft 03.1 of said motor 03 to the metering disc 02. In turn, saidhollow motor shaft 03.1 is fluidly connected to the vacuum generatingmeans (not shown) through an air extraction outlet 05. Thus, fluidconnection between the vacuum chamber and the vacuum generating means isachieved (not shown).

Seeds 07 are loaded into a reservoir 21 within the atmospheric pressurechamber through a seed inlet 06, which may or may not comprise a hopperand/or closure means (not shown).

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The sealingmember 15 is arranged over the face of the metering disc 02 so as tooverlap the vacuum chamber over some, but not all, the radially spacedholes 19.

The holes 19 utilize the vacuum in the overlapping vacuum chambergenerated by the vacuum generating means to capture seeds 07 from theseed reservoir 21 and retain them until the vacuum is interrupted,releasing the seed 07 from the holes 19 of the metering disc 02,preferably into a seed outlet 10. Interruption of the vacuum affecting aspecific hole 19 is achieved by rotating the metering disc 02 until saidspecific hole no longer overlaps with the vacuum chamber, thus releasingthe captured seed.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity 17 within the housing 01, which doubles both as a cleaning devicefor cleaning and removing obstructions in the holes 19 and as anauxiliary means for releasing seeds 07 not properly released by the seedreleasing mechanism. Preferably, the toothed wheel 11 is made fromflexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the seed holes 19 in the meteringdisc 02, and not removed by the curved plate 08, are carried over by therotating metering disc 02 until their respective seed holes 19 no longeroverlaps with the vacuum chamber, thus releasing the seeds 07 from themetering disc 02 and allowing them to freely fall through a seed outlet10, through a conducting means to an opened furrow on the soil oranother section of the seeding equipment.

Embodiment 8

FIGS. 15 and 16 show a pressure seed metering device according to aneighth embodiment of the present invention. Said pressure seed meteringdevice comprises a cylindrical housing 01, which houses a rotatingmetering disc 02 coaxially coupled about its central axis to an annularrotor 03.1 of a coaxially arranged large diameter torque motor 03 bymeans of a hollow hub 13 or other suitable coupling means which allowthe passage of air through it. The annular stator 03.2 of the largediameter torque motor 03 is fixed to the interior of the housing 01 bysuitable fastening means (not shown). The hollow hub 13 is coupled tothe annular rotor 03.1 by rods or pins 14 or other suitable fasteningmeans. The metering disc 02 is coupled to the hollow hub 13 by suitablesecuring means. In a preferred embodiment, the metering disc 02 issecured to the hollow hub 13 by means of a cotter pin 12 secured about amain central rod of the hollow hub 13 and a plurality of radiallydisplaced lesser pins 24 secured about secondary fastening rods on thehub 13.

The metering disc 02 divides the housing 01 into two chambers; apositive pressure chamber, fluidly connected to a blowing means (notshown), and an atmospheric pressure chamber. Seeds 07 are loaded into areservoir 21 within the positive pressure chamber through a seed inlet06, which may or may not comprise a hopper and comprises sealing means(not shown). Pressure is created in the positive pressure chamber by thepressurization of air in said chamber by means of a blowing means (notshown), such as an air compressor, through a pressurized air inlet 05.Fluid connection between the blowing means and the positive pressurechamber in the housing 01 is achieved through a plurality of orifices orholes 18 in the hollow hub 13 which connects the annular rotor 03.1 ofthe large diameter torque motor 03 to the metering disc 02. In turn, theannular rotor 03.1 is fluidly connected to the pressurized air inlet 05,which is connected to the blowing means (not shown).

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the pressure generated in the positive pressure chamber by theblowing means to capture seeds 07 from the seed reservoir 21 and retainthem until the pressure is interrupted by a wheel 09 or other suitableseed releasing means, releasing the seed 07 from the holes 19 of themetering disc 02, preferably into a seed outlet 10.

In a preferred embodiment the wheel 09 comprises a device arranged toblock or isolate the affected holes 19 from the pressure generated bythe blowing means, causing the seed to be released from said affectedhole 19. Preferably, the wheel 09 is made from a flexible material, likerubber or other polymeric material, and located on the side of themetering disc 02 opposite to the seeds 07, which can isolate aparticular hole 19 from the pressure source.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity (not shown) within the housing 01, which doubles both as acleaning device for cleaning and removing obstructions in the holes 19and as an auxiliary means for releasing seeds 07 not properly releasedby the seed releasing wheel 09. Preferably, the toothed wheel 11 is madefrom flexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the wheel 09, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

Embodiment 9

FIGS. 17 and 18 show a vacuum seed metering device according to an ninthembodiment of the present invention. Said vacuum seed metering devicecomprises a cylindrical housing 01, which houses a rotating meteringdisc 02 coaxially coupled about its central axis to an annular rotor03.1 of a coaxially arranged large diameter torque motor 03 by means ofa hollow hub 13 or other suitable coupling means which allow the passageof air through it. The annular stator 03.2 of the large diameter torquemotor 03 is fixed to the interior of the housing 01 by suitablefastening means (not shown). The hollow hub 13 is coupled to the annularrotor 03.1 by rods or pins 14 or other suitable fastening means. Themetering disc 02 is coupled to the hollow hub 13 by suitable securingmeans. In a preferred embodiment, the metering disc 02 is secured to thehollow hub 13 by means of a cotter pin 12 secured about a main centralrod of the hollow hub 13 and a plurality of radially displaced lesserpins 24 secured about secondary fastening rods on the hub 13.

The metering disc 02 divides the housing 01 into two chambers; a vacuumchamber, fluidly connected to a vacuum generation means (not shown), andan atmospheric pressure chamber. Seeds 07 are loaded into a reservoir 21within the atmospheric pressure chamber through a seed inlet 06, whichmay or may not comprise a hopper and/or closure means (not shown).Vacuum is created in the vacuum chamber by the extraction of air in saidchamber by means of a vacuum generating means (not shown) through an airextraction outlet 05. Fluid connection between the vacuum generatingmeans and the vacuum chamber in the housing 01 is achieved through aplurality of orifices or holes 18 in the hollow hub 13 which connectsthe annular rotor 03.1 of the large diameter torque motor 03 to themetering disc 02. In turn, the annular rotor 03.1 is fluidly connectedto the air extraction outlet 05, which is connected to the vacuumgenerating means (not shown).

The metering disc 02 comprises a plurality of radially spaced holes 19or other suitable seed retaining means on its outer region. The holes 19utilize the vacuum generated in the vacuum chamber by the vacuumgenerating means to capture seeds 07 from the seed reservoir 21 andretain them until the vacuum is interrupted by a wheel 09 or othersuitable seed releasing means, releasing the seed 07 from the holes 19of the metering disc 02, preferably into a seed outlet 10.

In a preferred embodiment the wheel 09 comprises a device arranged toblock or isolate the affected holes 19 from the vacuum generated by thevacuum generating means, causing the seed to be released from saidaffected hole 19. Preferably, the wheel 09 is made from a flexiblematerial, like rubber or other polymeric material, and located on theside of the metering disc 02 opposite to the seeds 07, which can isolatea particular hole 19 from the vacuum source.

The embodiment further comprises a suitable curved plate 08 or othersingulating means to prevent the simultaneous retention and discharge oftwo or more seeds 07 from a single hole 19, by removing excess seeds andreturning them to the seed reservoir 21. Additionally, the embodimentfurther comprises a toothed wheel 11 with a plurality of teeth orprojections, or other suitable auxiliary ejector means, arranged in acavity 17 within the housing 01, which doubles both as a cleaning devicefor cleaning and removing obstructions in the holes 19 and as anauxiliary means for releasing seeds 07 not properly released by the seedreleasing wheel 09. Preferably, the toothed wheel 11 is made fromflexible material, like rubber or other polymeric material.

In operation, seeds 07 captured by the metering disc 02, and not removedby the curved plate 08, are carried over to the wheel 09, which in turnreleases the seeds 07 from the metering disc 02 and allows them tofreely fall through a seed outlet 10, through a conducting means to anopened furrow on the soil or another section of the seeding equipment.

The above embodiments should not to be taken as limiting examples of theinvention, as the benefits of the application of a direct drive seedmetering device driven by a DC brushless toroidal torque motor, asdisclosed herein, in other embodiments of seed metering devices will beapparent to those skilled in the art. Thus, the invention is furthersuited for its application on other seed metering devices as, forexample, devices without a pressure or vacuum source and which utilizeother types of seed capturing, retaining and releasing means, such asteeth, cells, cradles and the like.

1. Seed metering device for a row crop sowing machines, also called seedplanters, comprising a seed metering disc rotatable about a centralshaft, having a plurality of seed capturing and retaining means forcapturing and retaining the seeds, a motor, which drives the seedmetering disc, releasing means for releasing the seeds from the seedcapturing and retaining means, conducting means for conducting thereleased seeds onto the ground, and a housing for containing andprotecting the metering disc, wherein the motor is of the hollow-shafttype, toroidally shaped and coaxially coupled to the metering disc.
 2. Ametering device according to claim 1, wherein the hollow-shaft motor isa direct drive DC motor of the brushless type.
 3. A metering deviceaccording to claim 1, wherein the seed capturing and retaining means areselected from the group comprising holes, cells or cradles located nearthe outer perimeter of the metering disc.
 4. A metering device accordingto claim 1, wherein the seed capturing and retaining means consist ofholes located near the outer perimeter of the metering disc and the holesize is determined by the type of seed to be sown, so as to be able toretain the seeds in place until reaching the releasing means.
 5. Ametering device according to claim 1, wherein the metering disc is acogwheel or gear, the teeth of which are the seed capturing andretaining means, where the teeth shape and the size of the gap betweenthe teeth being determined by the type of seed to be sown, so as to beable to retain the seeds in place until reaching the releasing means. 6.A metering device according to claim 1, wherein the housing containingthe metering disc forms a vacuum chamber together with one of the facesof the metering disc, the device being provided with vacuum generatingmeans for lowering the air pressure on said face of the metering disc soas to capture and retain the seeds within the seed capturing andretaining means arranged on the face of the metering disc opposite thevacuum chamber.
 7. A metering device according to claim 1, wherein thehousing containing the metering disc forms a high pressure chambertogether with one of the faces of the metering disc, the device beingprovided with blowing means for increasing air pressure on said face ofthe metering disc so as to capture and retain the seeds within the seedcapturing and retaining means arranged on the same face of the meteringdisc.
 8. A metering device according to claim 1, wherein the devicefurther comprises a flexible sealing member contained within thehousing, which is sealingly attached to the inner wall of the housingand which is sealingly pressed against one face of the metering disc,thus defining a vacuum chamber, the device being provided with vacuumgenerating means for lowering the air pressure on said vacuum chamber soas to capture and retain the seeds within the seed capturing andretaining means arranged on the face of the metering disc opposite thevacuum chamber.
 9. A metering device according to claim 1, wherein thedevice further comprises a concave plate within the housing, sealinglyattached to one face of the seed metering disc, and coupled to thehollow shaft of the motor, thus defining a rotatable vacuum chamber,vacuum generating means, a non-rotatable tube or conduit, non-rotatablyattached to the housing, which passes through the housing and the hollowshaft of the motor into the rotatable vacuum chamber, fluidly connectingthe vacuum means to the rotatable vacuum chamber.
 10. A metering deviceaccording to claim 6, wherein the motor is coupled to the seed meteringdisc by means of a hollow hub or other suitable coupling meanscomprising a hollow shaft or tube, and wherein the hollow hub isperforated, fluidly connecting the vacuum chamber to the hollow motorshaft of the motor coupled to said hollow hub.
 11. A metering deviceaccording to claim 6, wherein the vacuum generating means are fluidlyconnected to the vacuum chamber through the hollow motor shaft of themotor and through the perforated hollow hub.
 12. A metering deviceaccording to claim 6, wherein the vacuum generating means are fluidlyconnected to said vacuum chamber through an opening or orifice in thehousing in a position other than the hollow shaft—eccentricallyregarding the metering disc—and wherein the coupling means coupling themotor to the seed metering disk does not allow fluid connection betweenthe vacuum chamber and the hollow shaft of the motor.
 13. A meteringdevice according to claim 9, wherein the releasing means comprises aplate, fixed to the non-rotatable tube or conduit and located within therotatable vacuum chamber, which makes contact with a region of the faceof the metering disc inside the rotatable vacuum chamber, blocking theorifices of the seed capturing and retaining means and thereforeinterrupting the vacuum applied to the seeds retained on the other faceof the metering disk, making them drop into the conducting means towardsthe ground.
 14. A metering device according to claim 8, wherein thevacuum chamber does not simultaneously overlap with all the seedcapturing and retaining means of the metering disc and wherein therelease of the seeds from the holes of the seed capturing and retainingmeans occurs when a particular hole of the seed retaining means nolonger overlaps with the vacuum chamber.
 15. A metering device accordingto claim 6, wherein the seed releasing means comprises a rotatable wheelcontacting the metering disc on the face opposite the seeds capturingand retaining means, the wheel blocking the holes of the seed capturingand retaining means and therefore interrupting the vacuum applied to theretained seeds, making them drop into the conducting means towards theground.
 16. A metering device according to claim 1, wherein the motor ishoused within the housing, fixed to the inner surface of the housingwall.
 17. A metering device according to claim 1, wherein the motor isfixed to the outer surface of the housing wall.
 18. A metering deviceaccording to claim 1, wherein the seed releasing means comprisestationary or mobile brushes that physically remove the seeds from theseed capturing and retaining means.
 19. A metering device according toclaim 1, wherein the device further comprises singulating means forallowing only one seed to be retained in each capturing and retainingmeans.
 20. A metering device according to claim 19, wherein thesingulating means comprise a plate, parallel to the metering disc andspaced apart so as to allow only one seed to be retained in eachcapturing and retaining means.
 21. A metering device according to claim1, wherein the conducting means for conducting the released seeds ontothe ground comprises a conveyor belt provided with bristles for guidingthe seeds to an outlet close to the soil and into an opened furrow inthe soil.
 22. A metering device according to claim 1, wherein theconducting means for conducting the released seeds onto the groundcomprises a tube for allowing the seeds to freely reach the soil bygravity, into an opened furrow in the soil.
 23. A metering deviceaccording to claim 1, wherein the seed capturing and retaining means ofthe seed metering disc comprises holes and the housing comprises arotatable toothed wheel with a plurality of teeth or projections, thatengage with said holes of the seed capturing and retaining means as thedisc rotates, removing obstructions and releasing seeds stuck in saidholes.
 24. A metering device according to claim 1, wherein the motor isa large diameter annular torque motor with an annular rotor.
 25. Ametering device according to claim 7, wherein the motor is coupled tothe seed metering disc by means of a hollow hub or other suitablecoupling means comprising a hollow shaft or tube, and wherein the hollowhub is perforated, fluidly connecting the high pressure chamber to thehollow motor shaft of the motor coupled to said hollow hub.
 26. Ametering device according to claim 8, wherein the motor is coupled tothe seed metering disc by means of a hollow hub or other suitablecoupling means comprising a hollow shaft or tube, and wherein the hollowhub is perforated, fluidly connecting the vacuum chamber to the hollowmotor shaft of the motor coupled to said hollow hub.
 27. A meteringdevice according to claim 7, wherein the blowing means are fluidlyconnected to the high pressure chamber through the hollow motor shaft ofthe motor and through the perforated hollow hub.
 28. A metering deviceaccording to claim 8, wherein the vacuum generating means are fluidlyconnected to the vacuum chamber through the hollow motor shaft of themotor and through the perforated hollow hub.
 29. A metering deviceaccording to any one of claim 7, wherein the blowing means are fluidlyconnected to said high pressure chamber through an opening or orifice inthe housing in a position other than the hollow shaft—eccentricallyregarding the metering disc—and wherein the coupling means coupling themotor to the seed metering disk does not allow fluid connection betweenthe high pressure chamber and the hollow shaft of the motor.
 30. Ametering device according to claim 8, wherein the vacuum generatingmeans are fluidly connected to said vacuum chamber through an opening ororifice in the housing in a position other than the hollowshaft—eccentrically regarding the metering disc—and wherein the couplingmeans coupling the motor to the seed metering disk does not allow fluidconnection between the vacuum chamber and the hollow shaft of the motor.31. A metering device according to claim 7, wherein the seed releasingmeans comprises a rotatable wheel contacting the metering disc on theface opposite the seeds capturing and retaining means, the wheelblocking the holes of the seed capturing and retaining means andtherefore interrupting the pressure applied to the retained seeds,making them drop into the conducting means towards the ground.
 32. Ametering device according to claim 8, wherein the seed releasing meanscomprises a rotatable wheel contacting the metering disc on the faceopposite the seeds capturing and retaining means, the wheel blocking theholes of the seed capturing and retaining means and thereforeinterrupting the vacuum applied to the retained seeds, making them dropinto the conducting means towards the ground.